Inflatable prostheses and methods of making same

ABSTRACT

A laminate useful as a component of a medical implant, for example, useful as a component of an inflatable tissue expander. The laminate includes a base layer, an intermediate layer, and a top layer. When used as a component of a tissue expander, the laminate enables an internal chamber pressure of about 2.5 psi with an expander exterior compressive force of about 40 lbs.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/949,998, filed on Nov. 24, 2015, which is a continuation of U.S.patent application Ser. No. 14/148,547, filed on Jan. 6, 2014, which isa continuation of U.S. patent application Ser. No. 13/105,715, filed onMay 11, 2010, now U.S. Pat. No. 8,636,797, issued Jan. 28, 2014, whichis a continuation-in-part of U.S. patent application Ser. No.13/021,523, filed on Feb. 4, 2011, which claims the benefit of U.S.Provisional Patent Application No. 61/301,910, filed on Feb. 5, 2010,and the benefit of U.S. Provisional Patent Application No. 61/409,440,filed on Nov. 2, 2010, the entire disclosure of each of theseapplications being incorporated herein in its entirely by thisreference.

BACKGROUND INFORMATION

The present invention generally relates to medical implants and morespecifically relates to inflatable prostheses, such as tissue expanders,suitable for implantation in a mammal.

Prostheses or implants for reconstruction and/or augmentation of thehuman body are well known.

Fluid filled prostheses, for example, mammary prostheses or breastimplants, are widely used to replace excised tissue, for example after aradical mastectomy, or to augment the body to improve surfaceconfigurations. Although there are many applications where these areused, the most common is the mammary prosthesis, used to augment orotherwise change the size or shape of the female breast.

A conventional saline-filled breast implant includes an outer shell ofseveral layers of silicone elastomer having a valve or fill port. Theprosthesis is typically implanted into the breast cavity in an empty oronly partially filled state. The implant is then inflated to its finalsize by means of the valve or fill port. This helps reduce the size ofthe needed incision, and enables a surgeon to adjust and evenmicroadjust the volume of the implant. Unfortunately, the valve or fillport is sometimes noticeable to the touch.

Many or even most implants are manufactured to a given size and shape,and are implanted without means or expectation of changing their sizeafter implantation or initial filling when first inserted into thebreast. However, in many situations it is desirable to be able to adjustthe size of the implant over a substantial period of time. If the volumecan later be adjusted, an implant of lesser initial volume can beimplanted, and as the post-surgical swelling goes down, the implant usedas a prosthesis can be enlarged. Also, because often the procedure isfor cosmetic purposes, it is useful to be able to make a lateradjustment of size without having to replace the prosthesis with one ofa different size, which would require a subsequent surgical procedure.

One problem with many conventional adjustable implants is that theyrequire a valve to be part of the implant.

It would be advantageous to provide an adjustable volume implant whichdoes not require a valve or other access port for receiving fluid foradjustment.

Prior to implantation of a more permanent prosthesis, it is commonpractice to utilize a more temporary implant, for example, what is knownas a “tissue expander” in order to gradually create the space necessaryfor the more permanent prosthesis. Keeping living tissues under tensionby means of a tissue expander causes new cells to form and the amount oftissue to increase. Conventionally, a tissue expander comprises aninflatable body, having an inflation valve connected thereto. The valvemay be formed into the inflatable body itself or may be remotely locatedand connected to the inflatable body by means of an elongated conduit.

The inflatable body of the tissue expander is placed subcutaneously inthe patient, at the location of where tissue is to be expanded. Theinflation valve, whether on the implant or remote thereto, is alsosubcutaneously positioned or implanted, and is configured to allowgradual introduction of fluid, typically saline, into the inflationbody, by injection with a syringe. After gradual inflation atpre-determined intervals, the skin and subcutaneous tissues overlyingthe expander are consequently caused to expand in response to thepressure exerted upon such tissues by the inflatable body as solution isgradually introduced therein.

After gradual inflation at pre-determined intervals, which may extendover weeks or months, the skin and subcutaneous tissue will expand tothe point where further medical procedures can be performed, such as thepermanent implantation of a prosthesis, plastic and reconstructivesurgery, or for use of the skin and subcutaneous tissue for use in someother part of the body.

During a mastectomy, a surgeon often removes skin as well as breasttissue, leaving the remaining chest tissues flat and tight. To create abreast-shaped space for a reconstructive implant, a tissue expander issometimes used as described above.

In any event, it should be appreciated that locating the fill valve on aprosthesis such as a tissue expander or adjustable implant requiresconsiderable practitioner skill. Attempts to make products whichfacilitate this include the development of various products havingstructure, for example, embedded magnets or a raised ring, for assistingphysicians in locating the valve.

It has also proven difficult to develop a flexible protective materialthat is effective as a puncture resistant material while also being safefor implantation in the body. A puncture resistant material used as acomponent of a breast implant or tissue expander would ideally besufficiently flexible such that the implant could still be folded orrolled and inserted through a small incision while also providingresistance to needle punctures aimed at inflating the implant/expanderto its final size.

Bark et al., U.S. Pat. No. 5,066,303 discloses a self-sealing tissueexpander with a shell having a flowable sealing material. According toBark et al., fluid infusion into the shell can be done directly throughthe shell, without the need for a fluid entry port.

Schuessler, U.S. patent application Ser. No. 12/543,795, filed on Aug.19, 2009, the entire disclosure of which is incorporated herein by thisspecific reference, discloses a fluid filled implant including aself-sealing shell.

There is a need for improved temporary tissue expanders, more permanentadjustable implants, and other inflatable prostheses. The presentinvention addressed this need.

SUMMARY OF THE INVENTION

The invention relates to expandable prostheses, for example, implantsand tissue expanders, and in particularly to implantable temporarytissue expanders as well as more permanent mammary prostheses.

Accordingly, the present invention provides implants, for example butnot limited to tissue expanders and more permanent prostheses, forexample, those implantable in a breast, and methods of making same. Thepresent invention provides inflatable prosthetic implants, componentsthereof and methods of making same. In one aspect of the invention,inflatable prosthetic implants are provided which include, as acomponent of such implants, flexible, puncture resistant materials.

In another broad aspect of the invention, inflatable implants orprostheses, for example, tissue expanders and adjustable implants areprovided which generally comprise a puncturable, self-sealing anteriorportion, or shell, a puncture resistant posterior portion substantiallyopposing the anterior portion, and a fillable cavity defined between theanterior portion and the posterior portion.

It is to be appreciated that the terms “implant” “prosthesis” and“tissue expander” as used herein are intended to encompass permanentimplants, including adjustable implants, as well as relatively temporarytissue expanders, and components, for example, shells, of suchimplantable devices.

In one aspect of the invention, a method of making an inflatable deviceor prosthesis, suitable for implantation in a mammal, is providedwherein the method generally comprises the steps of providing aplurality of mesh segments, positioning the plurality of segments on acurved molding surface, applying a fluid elastomeric material to themolding surface with the segments positioned thereon, and allowing theelastomeric material to set to form a flexible shell having an open end,the shell including the fabric segments embedded within the setelastomer, and the shell being useful as a component of an inflatableprosthesis. The step of positioning may substantially entirely coveringthe molding surface with the mesh segments, for example, in a mannersuch that the mesh segments overlap one another. The method furthercomprises the step of sealing the open end of the elastomeric shell, forexample, by providing a puncture resistant member and sealing thepuncture resistant member to the open end of the elastomeric shell.

In one embodiment, the mesh segments comprise a non-stretchable meshfabric, for example, a substantially non-expanding polyester fabricmesh. In another embodiment, the mesh segments comprise a stretchablemesh fabric.

The method may further comprise the step of applying a tacky material tothe curved molding surface prior to the step of positioning the mesh.The tacky material may be a fluid elastomeric material, for example, asilicone dispersion.

In another embodiment, the method comprises pre-shaping, for example,thermoforming, a mesh element, from a two-dimensional sheet into a threedimensional “sock” having the general shape of the molding surface. Themethod includes positioning the pre-shaped mesh element onto the moldingsurface, applying a fluid elastomeric material to the molding surfacewith the pre-formed mesh positioned thereon, and allowing theelastomeric material to set to form a flexible shell having an open end,the shell including the preformed mesh embedded within the setelastomer, and the shell being useful as a component of an inflatableprosthesis.

In another aspect of the invention, an inflatable prosthesis made by themethods described herein is provided.

Further, in another aspect, an inflatable prosthesis in accordance theinvention generally comprises an interior shell defining an inflatablechamber, an exterior shell comprising a silicone-based elastomermaterial having a mesh embedded therein, a gel separating the interiorshell and the exterior shell, and a puncture resistant member forming abase of the prosthesis.

In yet another aspect of the invention, a method of making a needleguard for an inflatable prosthesis suitable for implantation in a mammalis provided. The method generally comprises the steps of providing afirst layer of puncture resistant members, for example, elongatedslates, providing a second layer of puncture resistant members such thatthe second layer of members overlies and is offset from the first layerof members, molding or otherwise applying a flexible material to thefirst layer of members and the second layer of slats to form a deviceuseful as a needle guard for an inflatable prosthesis. The step ofapplying or molding includes coupling the members to, for example,encasing the members within, the flexible material.

In one embodiment, the members are elongated slats, and the slats of thefirst layer are substantially parallel to the slats of the second layer.The slats may be made of any suitable puncture resistant material, forexample, a material selected from the group of materials consisting ofacetal, nylon, and polycarbonate. In some embodiments, the slats aremade of a metal, for example, stainless steel, aluminum or titanium. Theslats may be individual, separate elements that are cut from a sheet ofmaterial using any suitable means such as laser cutting. In otherembodiments, at least one of the first layer of slats and the secondlayer of slats comprises a single sheet, undivided sheet of materialhaving grooves defining the adjacent slats.

In some embodiments, the step of applying a flexible material comprisesapplying an elastomeric sheet between the first layer of slats and thesecond layer of slats, for example, applying an uncured elastomericsheet between the first layer of slats and the second layer of slats,and subsequently curing the sheets.

Alternative to the first and second layers of slats, it is contemplatedthat a puncture-resistant fabric may be used, for example, inconjunction with an elastomeric layer, to form a suitable needle guard.

In one aspect of the invention, a method for making an inflatableprosthesis suitable for implantation in a mammal is provided, whereinthe method comprises providing a needle guard made by a method of theinvention as described elsewhere herein and securing a flexible,inflatable shell to the needle guard.

In another aspect of the invention, an inflatable prosthesis is providedgenerally comprising a flexible shell forming an anterior surface of theprosthesis, wherein the needle guard forms at least a portion of aposterior surface of the prosthesis, and comprises a elastomer portionand a first layer of puncture resistant slats embedded in the elastomerportion. The needle guard may further comprise a second layer ofpuncture resistant slats. In some embodiments, the second layer of slatsis offset from the first layer of slats.

In yet another aspect of the invention, flexible, resilient punctureresistant assemblies are provided, the assemblies being, useful ascomponents of surgical implants, for example, but not limited to, needleguards as components of inflatable implants that are accessed with aneedle and syringe. Such implants for which the present materials areuseful include inflatable tissue expanders. Other implants that canbenefit from the present invention include fluid access ports whichinclude a fluid reservoir and needle penetrable septum. In these andother implantable devices, puncture resistant or puncture proofassemblies of the invention can be highly beneficial, for example, as ameans for preventing a needle tip from penetrating other areas of thedevice that are not intended to be punctured. Other beneficial uses forthe present assemblies will become more apparent upon reading thepresent specification, and are considered to be included within thescope of the invention.

For example, puncture resistant assemblies are provided which areflexible and/or formable into desired configurations.

In some embodiments, puncture resistant assemblies are provided whichare both flexible and resilient. Some of the present assemblies have thecharacteristic of shape memory, such that after being rolled or folded,they can resume an original shape or configuration. This aspect of theinvention is particularly, but certainly not exclusively, useful forapplication in a surgical environment, in which the assembly may be inthe form of a puncture proof material is rolled or folded into a narrowconfiguration, thereby enabling insertion thereof through a relativelysmall incision. Advantageously, some of the assemblies of the inventionare structured to be able to automatically resume an original,pre-deformed shape, for example, automatically, once the material is atthe desired implantation site.

In one embodiment of the invention, a puncture resistant assembly isprovided which generally comprises a first composite guard, a secondcomposite guard, and a intermediate layer securing the first and secondcomposite guards together and/or containing the first and secondcomposite guards.

Each of the first and second composite guards generally comprises anarrangement of puncture resistant elements or members, and a flexiblesubstrate on which the members are secured and positioned, generally ina spaced-apart relationship.

The members may be in the form of domes or plates. The members have ahardness effective to resist penetration, puncture or breakage uponforceful contact with a sharp surface, for example, a tip of a needle,an edge of a cutting implement such as a scalpel or knife, or the like.The members may be made of any suitable material, such as a hardmoldable substance, for example, a high durometer elastomer, polymer orrubber. Other suitable materials include metals, ceramics, and alloysthereof.

The flexible substrate on which the members are disposed may comprise afabric, mesh, film, elastomer, or other material.

Notably, the first composite guard and the second composite guard aredisposed with respect to one another such that the arrangement ofmembers of the first composite guard is offset or misaligned withrespect to the arrangement of members of the second composite guard. Insome embodiments, a third composite guard is provided. The thirdcomposite guard may be positioned with respect to the first and secondcomposite guards such that the members of the third composite guard aremisaligned with the members of at least one of the first and secondcomposite guards.

Advantageously, the misaligned or overlapping members of the adjacentcomposite guards provide a puncture resistant, or puncture proof, areawhile not significantly sacrificing flexibility of the assembly as awhole. That is, the composite guards may be arranged such that there areno significant gaps between individual puncture resistant members. Itcan be appreciated that depending upon the use of the final assembly,there may be some gaps between members so long as the gaps aresufficiently narrow to resist or prevent penetration by the type ofinstrument that the assembly is intended to be protected againstpuncture from.

In any event, in some embodiments of the invention, the punctureresistant members of the composite guards may provide a area ofprotection that substantially entirely covers a first side of the needleguard assembly.

The assembly may further comprise a intermediate layer, for example, anelastomer, securing together the first and second composite guards suchthat the members maintain their offset relationship. The intermediatelayer may be located between adjacent composite guards and may be bondedthereto. In one embodiment, the intermediate layer seals the flexiblecomposite members together and encapsulates the composite guards. Forexample, the intermediate layer may be an fluid tight barrier containingthe two or more layered composite guards. In some embodiments, theintermediate layer exhibits a springiness and resiliency or provides ashape memory characteristic to the assembly.

In another aspect of the invention, a method of making a needle guardassembly is provided wherein the method generally comprises the steps ofproviding first and second composite guards where each composite guardincludes a layer of puncture resistant members secured to a flexiblesubstrate and bonding the first composite guard with the secondcomposite guard in such that the members of the first composite guardare misaligned with the members of the second composite guard. In someembodiments, the method includes the step of bonding a third compositeguard to the second composite guard such that the members of the thirdcomposite guard are misaligned with the members of at least one of thefirst composite guard and the second composite guard.

In some embodiments, the method may comprise the step of providing anintermediate layer between the composite guards. In some embodiments,the method may comprise the step of encasing or encapsulating thecomposite guards in a fluid tight seal.

In one embodiment, an inflatable prosthesis is provided which comprisesan inflatable portion including an interior shell, an exterior shellcomprising a silicone-based elastomer material having a mesh embeddedtherein and a gel separating the interior shell and the exterior shell.The prosthesis further comprises a needle guard assembly comprising afirst composite guard and a second composite guard, each composite guardincluding an arrangement of puncture resistant members and a flexiblesubstrate having a first side on which the puncture resistant membersare disposed in a spaced apart fashion. The first composite guard andthe second composite guard are positioned such that the arrangement ofpuncture resistant members of the second composite guard are misalignedwith the arrangement of puncture resistant members of the firstcomposite guard. The needle guard assembly further comprises anintermediate layer disposed between and connecting the first compositeguard with the second composite guard.

In one aspect of the invention, the shell of the prosthesis comprises aself-sealing laminate defining an interior chamber of the prosthesis.The laminate generally includes a base layer formed from an elastomer, alayer of silicone of sufficient thickness for self-sealing of a needlehole therethrough and a top layer formed from an elastomer. The laminatemay have a total thickness for enabling an internal chamber pressure ofabout 2.5 psi within an expander exterior compressor force of about 40lbs.

More specifically, the laminate in accordance with this embodimentincludes base and top layers formed from one type of silicone elastomerand an intermediate layer disposed between the base and top layers,formed of another type of silicone elastomer. For example, the base andtop layers may be formed of Nusil PN-3606-1 and the intermediate layermay be formed of Nusil MED 6350.

In an exemplary embodiment, the base layer has a thickness of about0.006 inches, the top layer has a thickness of about 0.006 inches, andthe intermediate layer has a thickness of between about 0.100 inches and0.120 inches.

An additional layer, for example, a polyester mesh layer, may also beprovided as a part of the laminate to insure integrity of the tissueexpander.

Each and every feature described herein, and each and every combinationof two or more of such features, is included within the scope of thepresent invention provided that the features included in such acombination are not mutually inconsistent.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be more clearly understood and certain aspectsand advantages thereof better appreciated with reference to thefollowing Detailed Description when considered with the accompanyingDrawings of which;

FIG. 1 is cross-sectional view of a tissue expander in accordance withan embodiment of the invention, the tissue expander shown as implantedin a breast of a human being;

FIG. 2 is magnified view of a portion of the expander shown in FIG. 1;

FIG. 3 is a cross-sectional view of another tissue expander inaccordance with the invention;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3;

FIGS. 4A and 4B are a simplified top view and cross sectional view,respectively, of a needle guard feature of the tissue expanders of thepresent invention;

FIG. 5 is a cross-sectional view of another tissue expander inaccordance with the invention;

FIG. 6 is a cross-sectional view of yet another tissue expander inaccordance with the invention;

FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 6;

FIGS. 8-10 show steps useful in making some of the tissue expanders ofthe present invention;

FIG. 11 is cross-sectional view of another inflatable prosthesis of theinvention including a puncture resistant assembly;

FIG. 12 is an exploded view of the prosthesis shown in FIG. 11 in orderto illustrate certain components of the puncture resistant assembly;

FIG. 13 is a top view of a composite guard which is a component of thepuncture resistant assembly shown in FIG. 11;

FIG. 14 is a magnified view of a portion of the composite encompassed byline 14 of FIG. 13;

FIG. 15 is a cross-sectional view of the composite guard taken alongline 15-15 of FIG. 14;

FIG. 16 is a cross-sectional view, similar to the view shown in FIG. 15,of an alternative composite guard in accordance with certain aspects ofthe invention;

FIG. 16a is a cross-sectional view, similar to the view shown in FIG.15, of yet another composite guard in accordance with certain aspects ofthe invention;

FIGS. 17-19 illustrate steps useful in making some of the punctureresistant assemblies of the present invention;

FIG. 20 is a cross sectional representation of a closed self-tissueexpander shell comprising a laminate, in accordance with one embodimentof the present invention;

FIG. 21 is an enlarged cross sectional view taken along the line 21 ofFIG. 20 more clearly representing the configuration of the laminate ofthe shell shown in FIG. 20; and

FIG. 22 is a frequency/G′,G″ chart showing properties of a preferredmaterial for an intermediate layer of laminate of the embodiment shownin FIGS. 20 and 21.

DETAILED DESCRIPTION

The present invention generally pertains to implantable inflatabledevices and methods for making same, for example; devices such as softfluid-filled implants, for example, but not limited to, permanent ortemporary implants useful in breast reconstruction or breastaugmentation procedures.

Turning now to FIG. 1, an inflatable device, in accordance with oneembodiment of the invention, is shown generally at 10, as implanted in ahuman breast 2. The device 10 is being inflated with a suitable fluid,such as a saline solution 14, by means of a typical syringe 18.

The device 10 generally comprises an inflatable portion 12 comprisingouter shell 22, an inner shell 24 and a intermediate layer 26therebetween. The inner shell 24 defines an inflatable cavity 28 (shownhere as being filled with saline solution 14).

Inflation of the cavity 28 causes expansion of the device as shown byarrows 30. The device 10 further includes a posterior portion 34 that isgenerally resistant to expansion upon inflation of cavity 28. The totalvolume of the device 10 is adjustable by introduction and removal offluid into and from the fillable cavity 28.

The outer shell 22 of the device 10 may comprise at least one layer ofelastomeric material, for example, a first layer 36 of elastomericmaterial and a second layer 38 of elastomeric material, and anadditional layer of a different material, for example a reinforcementlayer 40, located between the first and second layers 36, 38 ofelastomeric material.

The elastomeric material may be a silicone elastomer such as a dimethylsilicone elastomer, for example, a substantially homogeneousdimethyl-diphenyl silicone elastomer. One composition useful in thepresent invention is described in Schuessler, et al., U.S. applicationSer. No. 12/179,340, filed Jul. 24, 2008, the disclosure of which isincorporated herein in its entirety by this specific reference. Theelastomeric material may comprise a room temperature vulcanizing (RTV)or a high temperature vulcanizing (HTV) silicone from about 0.1-95 wt %,for example, about 1-40 wt %, for example, about 30 wt %. In anexemplary embodiment, the silicone-based fluid material is a hightemperature vulcanizing (HTV) platinum-cured silicone dispersion inxylene.

The reinforcement layer 40 may comprise a mesh or fabric, for example, asynthetic polymer mesh or fabric, for example, a mesh or fabric madefrom polyethylene terephthalate) (PET), polypropylene (PP), polyurethane(PU), polyamide (Nylon), polyethylene (PE), any other suitable material,or combinations thereof.

In an exemplary embodiment, the outer shell 22 is made by dipping two ormore layers of silicone-based elastomer over a conventional breastimplant mandrel, followed by placement of a pre-fabricated 2 or 4-waystretchable “sock” of the said reinforcing material layer 40, followedby two or more dips of the silicone-based elastomer. The reinforcing“sock” is able to take the shape of the mandrel and the fabric istrapped on both sides between the elastomer layers 36, 38. In thisembodiment, the stretchable pre-shaped “sock” (which may form thereinforcing layer 40 of outer shell 22) can be relatively easily mountedon the mandrel because of its flexibility and elasticity, making iteasier to manufacture a reinforced shell with the intended shape anddimensions of the mandrel. The entire assembly forming the outer shell22 is heated in an oven at a temperature and time suitable to cure thesilicone.

In one embodiment of the invention, the reinforcement layer 40 isprovided by forming a “sock” by using a cinch 40 a as illustrated inFIGS. 8 and 9. Alternatively, the reinforcement layer 40 is thermoformedinto “sock” by placing a single sheet of suitable material, for examplea non-stretchable mesh, over a curved molding surface, for example, amandrel, and gathering the mesh material at 40 b, as shown in FIG. 10.The gathered mesh material is shaped, for example, thermoformed, to takeon the 3-D shape of the mandrel.

Alternatively, rather than mesh sock, the reinforcement layer maycomprise a plurality of fabric or mesh segments which are positioned ona mandrel or other curved molding surface. The segments maysubstantially entirely cover the molding surface. The segments may bepositioned such that they overlap one another. The molding surface mayfirst be contacted with a tacky material, for example, contacted with orcoated with a silicone elastomer dispersion, to facilitate adherence ofthe segments thereto. An elastomeric material, such as an uncuredsilicone sheet or a silicone dispersion is applied to the moldingsurface with the segments positioned thereon. The elastomeric materialis allowed to set to form a flexible shell having an open end, the shellincluding the fabric or mesh segments embedded within the set elastomer,and the shell being useful as a component of an inflatable prosthesis.

Post-curing, the reinforced shell is removed from the mandrel, andanother elastomeric shell (which forms the inner shell 24) is placedinside the first shell (which forms the outer shell 22). The inner shell24 may be a typical unreinforced elastomeric shell, or alternatively maybe made similarly to that described above with respect to the outershell 22. The inner shell 24 may have the same or smaller size relativeto outer shell 22. The two shells 22, 24 are vulcanized close to theiropen base using, for example, a ring-shaped patch 44, thus forming aninter-shell compartment. The dual-shell assembly is mounted back on amandrel. The size of the mandrel can be the same as the one used for theinner shell fabrication or slightly larger. The latter would result in alaterally stressed inner shell with potentially enhanced sealingproperties.

In some embodiments of the invention, at least one of the inner shell 24and the outer shell 22 comprises an elastomeric material comprising asubstantially homogenous layer of a silicone elastomer comprising apolysiloxane backbone and having a minimum mole percent of at least 10%of a substituted or pendant chemical group that sterically retardspermeation of said silicone gel through the layer. More specifically, inthis embodiment, the silicone elastomer is a polydimethyl siloxane andthe pendant chemical group is one of a phenyl group, for example, adiphenyl group or a methyl-phenyl group, a trifluoropropyl group, andmixtures thereof. Such materials are described in detail in Schuessler,et al., U.S. patent application Ser. No. 12/179,340, filed on Jul. 24,2008, the entire disclosure of which is incorporated herein by thisspecific reference. This material may make up one or more layers of theshell(s) 22, 24.

After the inner shell 24 and outer shell 22 are bonded together, acavity formed therebetween is then filled with a material, for example,a flowable material, for example, a silicone gel. This may beaccomplished using any suitable means known to those of skill in theart. In one embodiment, the gel is introduced through a reinforcedsilicone plug on the outer shell 22. The silicone gel between the outerand inner shells 22, 24, forms the intermediate layer 26. After filling,the assembly made up of the inner shell 24, outer shell 22 andintermediate layer 26, is cured, for example, by exposing the assemblyto heat in an oven for a suitable length of time. The mandrel thatdefines the desired shape of the implant can be round or oval, with alower or upper pole for optimal projection. Before sealing the implantwith a patch, a needle guard element, such as that described and shownelsewhere herein, may be inserted and bonded to the inner shell 22and/or outer shell 24, to form the posterior portion 34 of the device.

It can be appreciated that the device 10, in the form of a tissueexpander, once implanted in a patient, must be repeatedly accessedduring the expansion process with percutaneous needle punctures, such asshown in FIG. 1. In some embodiments, the tissue expander devices areable to survive repeated puncturing and over-expansion to 200% by salinewithout leakage.

The device 10 can also be in the form of a more permanent mammaryprosthesis, for example an adjustable breast implant. The volume of theimplant can be adjusted in situ by accessing the cavity 28 with a needlethrough the self-sealing anterior portion of the device 10. In someembodiments, the cavity 28 has a small volume relative to the gelportion 26, to provide a comfortable implant having the desirablequalities of a gel-filled implant with the advantages of beingsize-adjustable with saline.

In summary, the anterior surface of the device 10 is self-sealing andcan be accessed for fluid communication. The mechanism of self-sealingis facilitated by a combination of the gel layer 26 and shell 22. Aftera void is created by a needle used to introduce filler (saline) into theimplant 10, the gel layer 26 prevents the saline 14 from having a directpath to the exterior and the reinforcing mesh 40 enhances this propertyby physically constraining the gel from expansion under pressure exertedby the saline 14. The reinforcing materials 40 include but are notlimited to meshes and fabrics made from PET, PP, PU, Nylon, etc. andcombinations thereof. This invention features a novel manufacturingmethod for shaping the implant shell into 2-D and 3-D structures makingit more convenient to manufacture and convert these reinforcedstructures into mammary prostheses.

In order to limit the depth of penetration of the needle, and also togive the medical professional feedback as to when the needle has reachedthe correct location for filling, conventional (prior art) tissueexpander devices sometimes include a rigid backing or needle stop behindthe filling port in the posterior side of the device. Typically theseneedle stops are made of metals or very hard or thick plastics toprevent needle penetration through the injection site. By nature then,these needle stops are quite rigid and inflexible, can be uncomfortable,and can limit the collapsibility of the device which affects ease ofinsertion of the expander through the initial incision.

In one aspect of the present invention, the posterior portion 34 ofdevice 10 may comprise an improved needle guard 50. The needle guard 50may comprise any suitable biocompatible polymer (e.g. PE, PP, PU, PET,PI, TPU, high durometer silicones, ABS etc.) that is strong enough toresist needle puncture. The needle guard 50 may comprise one or morelayers 56 of puncture resistant material with or without an intermediatelayer 58. In some embodiments, the needle guard 50 is structured so asto prevent, or substantially prevent, the device 10 from expandingtoward the chest wall during inflation of cavity 28.

For filling an implant of the present invention, syringe coupled to a 21g or smaller needle may be used. The needle may be introduced anywherein the anterior portion of the implant, such that it reaches the needleguard 50, where it is prevented from penetrating further. The implant isthen filled with saline or other liquids for tissue expansion. Afterremoval of the needle, the assembly (e.g. outer shell 22, inner shell 24and intermediate layer 24) self-seals and prevents the implant fromleaking.

In FIGS. 3 and 4, the needle guard 50 may comprise an elastomer portion62, and one or more layers of puncture resistant members coupledthereto. In the shown embodiment, members comprise elongated members,for example, slats 68 coupled to the elastomer portion 62.

In this case, the needle guard 50 comprises one or more layers of slats68, for example, a first layer 64 of slats 68 and a second layer 66 ofslats 68 coupled to the elastomer portion 62. As shown, the slats 68 ofthe first layer 64 overlap, or are offset from, the slats 68 of thesecond layer 66. For example, spacing between slats 68 of the firstlayer 64 are aligned with slats of the second layer and vice versa.Elastomer portion 62 may include grooves 69 or slots. Grooves may bealigned with slats 68 to facilitate rolling or folding of the device 10.

Slats 68 extend across substantially the entire posterior portion 34 andare aligned substantially parallel to one another. This arrangementallows the device 10 to be rolled or folded in alignment with the slats68 while the offset or overlapping positioning of the first and secondlayers 64, 66 provides protection in the event a needle enters spacing70 between adjacent slats 68.

Alternative to this arrangement, adjacent slats in each layer mayoverlap one another (not shown). The needle guard comprises overlappingbut independent small pieces of rigid puncture-resistant material, andlike the offset layers of slats 68 described and shown elsewhere herein,the overlapping configuration provide that there are no “line-of-sight”openings through which a needle can pass.

Slats 68 may be a polymer material. Slats may be, for example, nylon,acetal, polycarbonate, or other suitable, biocompatible, punctureresistant or puncture-proof polymeric material. Slats 68 may be metal,for example, stainless steel, aluminum or titanium.

In various exemplary embodiments, slats 68 may be between about 10 mm toabout 100 mm or more in length, about 2 mm to about 30 mm in width, andabout 0.2 mm to about 4 mm in thickness. Slats of other configurationsand dimensions suitable for achieving the desired flexibility of theneedle guard 50 may also be used. Such variations of materials anddimensions are considered to fall within the scope of the presentinvention. In one embodiment, slats 68 have a thickness of about 2 mmand the needle guard 50, including first and second layers 64, 66 ofslats 68 and elastomer material therebetween, has a total thickness of5.0 mm or less.

Slats 68 may be formed by laser cutting same from a sheet of material.Alternatively, slats 68 may be defined by grooves in a single sheet ofmaterial. In this specific example, the 2 layers of parallel slats ofpuncture-resistant plastic about 0.25″ wide and with about 0.05″ openspace between each slat. The layers are offset from each other so thatthe open space of one slat layer is centered on the middle of a slat inthe layer below. All the slats are encapsulated in a soft flexiblematerial like silicone. The open space between the slats gives the wholeassembly flexibility to be readily folded or rolled up even though theplastic itself is rigid and resistant to extensive bending. Other shapesand layering designs of independent pieces of puncture resistantmaterials would provide the needle stop with more and different degreesof bending and folding capability.

The rigid or semi-rigid material forming the slats could bethermoplastics such as acetal, nylon, polycarbonate, and others; or thinmetals such as stainless steels, aluminum, or titanium. The use ofplastics can be advantageous in that the entire device 10 can be made tobe MRI compatible.

In a similar aspect of the invention, thin elastomeric films (0.25 mm-1mm) made of materials resistant to needle punction may be used as acomponent of the needle guard portion of the implant. In someembodiments, such films can be provided with grooves in their design toallow folding/unfolding during insertion. The films may be attached tothe shell using adhesives or alternatively may be are encapsulated insilicone.

In another embodiment, rather than independent slats 68, one or morelayers of flexible “slat sheets” are provided. In this embodiment,adjoining slats could be made by starting with readily available sheetsof the desired plastic of the appropriate thickness. Parallel, adjacentslats are created by laser cutting through the plastic to create thedesired spacing between slats but not all the way to the edges of theplastic sheet, thereby leaving a material, for example, a border thatholds all the slats together. In this way the pre-cut slats can still behandled as one piece and therefore maintain the desired spacing andorientation. In one embodiment, two of these pre-cut plastic “slatsheets” are alternately layered between 3 sheets of silicone. Aftercuring the silicone, a die cutter of the desired shape of the needlestop can cut within the borders of the pre-cut slats to stamp out thefinished needle stop that now has many unconnected slats eachindependently encased in silicone.

Alternatively still, the pre-cut slat sheets could be held in thedesired orientation in a mold and silicone could be injected and curedaround them. Additional assembly steps could include creating a siliconeborder around the needle stop that would assemble to the expanderenvelope, texturing or adding features to the needle stop surface, orshaping the needle stop assembly so that it has a concave exterior tobetter fit the chest wall anatomy in the case of a breast tissueexpander.

Turning to FIGS. 4A and 4B, yet another variation of a needle guard 250is provided, similar to needle guard 50, except that rather than slats68, one or more layers of a puncture resistant mesh 152 are provided.Needle guard 150 may be substantially identical to needle guard 50described above, with one or more differences being as follows.

In the shown exemplary embodiment, the needle guard 150 comprises one ormore layers of mesh 152, for example, a single layer of mesh 152 coupledto, for example embedded in, the elastomer portion 162. In otherembodiments, not shown, two or more layers of mesh are provided, whereinfibers or cords making up the mesh, in adjacent layers of mesh, overlapone another. For example, interstices or spacing between mesh fiber of afirst layer of mesh aligns with the mesh fiber of a second layer ofmesh, and vice versa. Alternatively, a single layer of mesh is providedwith interstices between fibers being sized to prevent needlepenetration therethrough.

Flexibility of mesh 152 and elastomer portion 162 allow the entireimplant device to be rolled or folded upon insertion into a breastcavity through a small incision.

Mesh 152 may be a polymer or a metallic material. Mesh may be, forexample, a polymer such as nylon, acetal, polycarbonate, or othersuitable, biocompatible, puncture resistant or puncture-proof material.Mesh 152 may be metal, for example, stainless steel, aluminum ortitanium.

It should be appreciated that in many of the embodiments of the presentinvention, the needle guard making up the posterior portion of theimplant comprises puncture resistant members arranged in an overlappingconfiguration to provide no “line-of-sight” openings through which aneedle can pass. These puncture resistant members can be variouslyconfigured and arranged to achieve this goal.

In a preferred embodiment, it is desirable for the needle stop to beflexible for insertion yet rigid to resist needle puncture. To preventmovement of the needle guard inside the device the needle stop materialmay be adhered, fused or vulcanized to the posterior of the implant orthe patch. For this purpose, the needle guard may be dipped siliconethat is then heat cured, such that the needle guard is covered by asilicone sheath. This silicone sheath is vulcanized to the siliconepatch or posterior of the implant, to prevent movement of the guardinside the implant.

Another device 110 in accordance with the invention is shown in FIG.5-7. Device 110 may be substantially identical to device 10 except thatdevice 110 does not include an inner shell 24 or an intermediate layer26. Device 110 comprises a self-sealing outer layer 122. Self-sealingouter layer 122 may be identical to layer 22 of device 10. Further,rather than needle guard 50, device 110 comprises needle guard 128 whichcomprises a puncture resistant elastomeric member 130 having grooves 132for facilitating rolling or folding of device 110 during insertion.

Turning now to FIGS. 11-16 a, another device, for example, an inflatableimplant, in accordance with the invention is shown generally at 310.Implant 310 may be identical to implant 10 shown in FIG. 3, with theprimary difference being that instead of needle guard 50 made up oflayers of slats as described elsewhere herein, implant 310 includes apuncture resistant material 314 as shown and now described.

Device 310 includes a inflatable portion 312, and a puncture resistantassembly 314.

Device 310 is expanded or inflated (or deflated) by insertion of aneedle 313 (FIG. 1) through inflatable portion 312 (which may beidentical to inflatable portion 12 of device 10) and introduction offluid into a cavity 312 a. Instead of inflatable portion 12, it can beappreciated that inflatable portion 312 can include any suitablestructure, including an elastomeric bladder having an access port with aneedle penetrable septum, or may be made partially or entirely of apuncturable, but self sealing material. Some suitable self sealingmaterials are described, for example, in U.S. patent application Ser.No. 12/543,795, filed on Aug. 19, 2009, the entire specifications ofwhich are incorporated herein by this reference.

In order to prevent the needle 313 from undesirably penetrating throughthe device 310, the device is equipped with assembly 314.

Referring now to FIG. 12, the assembly 314 generally comprises a firstcomposite guard 316 and a second composite guard 318. In the shownembodiment, the assembly 314 further includes a third composite guard320. In other embodiments, only two composite guards or more than threecomposite guards are provided. An intermediate layer 324 is providedbetween adjacent guards, for example, between guard 316 and guard 318,and, likewise, between guard 318 and guard 320.

Turning now as well to FIGS. 13 and 14, each of composite guards 316,318, 320 includes a plurality of, for example, an arrangement, array, orpattern of, puncture resistant members 330, and a flexible substrate 332having a first side on which the puncture resistant members 330 aredisposed in a generally spaced apart fashion.

As can be perhaps best appreciated from FIG. 11 (and FIG. 19), the firstcomposite guard 316 and the second composite guard 318 are positionedsuch that the arrangement of puncture resistant members 330 of thesecond composite guard 318 are misaligned with the arrangement ofpuncture resistant members 330 of the first composite guard 316.Similarly, the second composite guard 318 and the third composite guard320 may be positioned such that the arrangement of puncture resistantmembers of the third composite guard 320 are misaligned with thearrangement of puncture resistant members of at least one of the firstcomposite guard 316 and the second composite guard 318. Thus,accordingly, the composite guards 316, 318, 320 are arranged relative toone another such that there are no straight line open spaces, orsubstantial gaps, between members 330 to allow a needle or sharpimplement to penetrate entirely through the assembly 314. Yet,advantageously, the assembly 314 as a whole may be quite flexible inthat the substrate 332 on which the spaced apart 330 members aredisposed is supple, flexible and/or bendable.

Turning specifically to FIG. 12, the intermediate layer 324 may comprisea flexible, connecting material which is effective to couple or bond thefirst composite guard 316 with the second composite guard 318, and thesecond composite guard 318 with the third composite guard 320. As shownin FIG. 12, the intermediate layer 324 is positioned between thearrangement of puncture resistant members 330 of the first layer 316 andthe flexible substrate 332 of the second layer 318, and anotherintermediate layer 324 is positioned between the arrangement of punctureresistant members 330 of the second layer 318 and the flexible substrate332 of the third layer 320.

The composite guards 316, 318, 320 may be identical to one another, andfor the sake of simplicity, only the first composite guard 316 will nowbe described, with the understanding that, in the shown embodiment, whatis described for the first composite guard 316 is also applicable tosecond composite guard 18 and third composite guard 320.

The members 330 may be any suitable shape. In FIG. 15, the members 330are somewhat dome shaped with rounded surfaces. In other embodiments,members 330 a may be planar as illustrated in FIG. 16. Alternativelystill, the members 330 b may include both rounded surface and planar orflat surfaces, such as the members 330 b which are dome shaped with aflat upper surface, as illustrated in FIG. 16 a.

The members 330 have a thickness of between about 0.1 mm and about 1.0mm, for example, a thickness of between about 0.2 mm and about 0.5 mmfor example, between about 0.1 mm and about 1.0 mm. The members 330 havea spacing of between about 0.2 mm and about 0.5 mm. The members 30 havea diameter of between about 0.5 mm and about 2.0 mm, for example, adiameter of about 1.5 mm.

In some embodiments, the guard 316 includes between about 50 and about1000 members per square inch (psi), for example, about 400 psi.

In a specific embodiment, the guard 316 include about 400 members psi,each having a diameter of about 1.5 mm and each being spaced apart about0.2 mm.

The members 330 (and 330 a and 330 b) are made of a suitable punctureresistant material, such as an epoxy, polymer, rubber, ceramic or metal,or suitable combination or alloy thereof. For some applications,suitable materials include polyethylene (PE), polypropylene (PP),polyurethane (PU), polyethylene terephthalate (PET), polycarbonate (PC),polyisoprene (PI), thermoplastic urethanes and thermoplasticpolyurethanes (TPU), high durometer silicones, acrylonitrile butadienestyrene (ABS) etc. In some embodiments, the members 330 are made ofmaterial selected from acetal, nylon, and polycarbonate. In someembodiments, the members 330 are made of a metal, for example, stainlesssteel, aluminum, titanium, or other metal.

The flexible substrate 332 may comprise a mesh, film, fabric, elastomer,or other suitable material.

The intermediate layer 324 may be a polymer, for example, an elastomericpolymer, for example, a silicone elastomer, for example, a low durometersilicone rubber.

In some embodiments, the assembly 314 has a resiliency or a shape memorysuch that it will restore from a folded or rolled configuration to anoriginal, different configuration. The original configuration may be agenerally flat or planar configuration. This may be provided by using asuitable intermediate layer material, such as a silicone elastomer thathas a shape memory characteristic.

Assembly of the guard assembly 314 may be accomplished as follows and asshown in FIGS. 17-19.

Turning now to FIG. 17, guard 316 generally comprising members 330 andsubstrate 332, is made by any suitable method, including stencilprinting, for example, using equipment and processes used in surfacemount technology/PCB fabrication. Other processes that can be used tomake the guard 316 include micro-dot dispensing and printing, laseretching. Other suitable methods will be known to those of skill in theart.

Turning to FIG. 18, intermediate layer 324 may be formed as follows. Asuitable material, for example, a sheet of uncured silicone, is placedon one side of the guard 316, for example, on the side having members 30and substrate 332. The sheet is then subjected to curing conditions tocause the sheet to adhere to the members 330, forming intermediate layer324 thereon. In the presently described example embodiment, this step isdone three times, with three separate guards 316, 318, 320, to form thecomponents 316′, 318′ and 320′ of assembly 314. (See FIG. 18a ).

The assembly 314 is then placed in an oven or otherwise subjected tofurther curing conditions to seal the assembly components together suchas shown in FIG. 19.

FIG. 20 shows an alternative shell 416 useful for forming a self sealingtissue expander or a more permanent prosthesis 410, in accordance withthe invention. Although not shown, it can be appreciated that the tissueexpander/prosthesis 410 can include a needle guard 50, 128, 316, forminga posterior surface of prosthesis 410, as described elsewhere herein.

In this embodiment, the shell 416 comprises a laminate 420 made up oflayered components, the laminate 420 being formable on a conventionalmandrel, using conventional techniques. The shell defines a cavity whichis fillable and expandable with a suitable fluid 420.

With reference to FIG. 21, the laminate 420 includes an elastomer baselayer 424, a layer 428 of silicone, which is sufficient thickness forself-sealing of a needle hole therethrough (not shown), and a top layer432 also formed from an elastomer.

The base and top layer 424, 432 may be formed of any suitablebiocompatible elastomer. In a specific embodiment, layers 424 and 432comprise any suitable silicone elastomer, for example, a siliconeelastomer marketed under the name MED 6400, available from NusilTechnology, Carpinteria, Calif. (Shore A 30, ultimate tensile strength1250 psi, % Elongation 900, tear strength 150 lbf/in.)

Preferably, the intermediate layer 428 is formed of a soft silicone gelhaving the viscoelastic properties (dynamic modulus G′,G″) of a productshown in the chart in FIG. 22, for example, a silicone elastomermarketed under the name MED 6350, also available from NuSil. Thispreferred material has dynamic modulus G′,G″ between Nusil MED 6400 anda cohesive silicone gel. In this chart, G′ represents storage modulus ofmaterial indicative of shape/dimensional stability, and G″ is lossmodulus of material indicative of flow within material.

The intermediate layer preferably comprises a material with storagemodulus at about 0.1, 1 and 10 Hz of about 4490, about 8330 and about18800 Pa, respectively. Further the material may have a loss modulus at0.1, 1 and 10 Hz of about 1840, about 4820 and about 12400 Pa,respectively, and a complex viscosity at 0.1, 1 and 10 Hz of about 7720,about 1520 and about 358 Pa·s. For example, the intermediate layer maybe Nusil MED 6350.

It has been found that when the base layer 24 has a thickness of about0.006 inches and a silicone layer 28 has a thickness of between about0.100 inches and 0.120 inches, and the top layer has a thickness ofabout 0.006 inches. An internal chamber pressure of about 2.5 psi can beestablished with expander exterior compressor force of about 40 lbs.

This is important in the effectiveness of the expander to expand tissue,not shown, without undue pressure, as may be the case with prior arttissue expanders. A mesh, for example, a polyester mesh 436 adjacent theintermediate layer, may be utilized for strengthening the laminate withthe polyester mesh having a thickness also about 0.006 inches.

As shown in FIG. 1, the tissue expander 10 includes no filling port areawith the entire expander 10 having a self-healing characteristics forsealing any hole created by a hypodermic needle when the saline 20filling process is complete and the needle is removed.

The materials of the present invention also enable mandrel forming ofthe expander 10.

In that regard, the expander 10 is formed on a mandrel (not shown)having a contoured surface that substantially conforms to a desiredshape of the tissue expander 10.

The base layer 24 is coated on the mandrel with a plurality of coats toestablish a thickness of about 0.006 inches. The silicone layer 28 isthereafter coated onto the base layer and mandrel and cured with athickness of about 0.1 inches to 0.12 inches. The mesh 36 may bedisposed over the silicone layer 28 and secured thereto by curing of thesilicone layer 28.

Thereafter the layer 32 is coated onto the underlying base layer,silicone layer, and mesh to a thickness of about 0.006 inches.

The layers 24, 28, 32 may be cured in a conventional manner.

As hereinabove noted, the total thickness of the base layer 24, siliconelayer 28, and top layer 32 enable an internal chamber pressure of about2.5 psi with an expander exterior compressor force of about 40 lbs.

While this invention has been described with respect to various specificexamples and embodiments, it is to be understood that the invention isnot limited thereto and that it can be variously practiced within thescope of the invention.

What is claimed is:
 1. A laminate suitable for use as a shell forflexible, fillable prosthesis, said laminate comprising: a base layer; atop layer; and an intermediate layer disposed between the base layer andthe top layer, the intermediate layer being a silicone elastomer ofsufficient thickness for self-sealing of a needle hole therethrough; atotal thickness of the base layer, intermediate layer and top layerenabling an internal chamber pressure of about 2.5 psi with an expanderexterior compressive force of about 40 lbs.
 2. The laminate according toclaim 1 wherein the intermediate layer comprises a material with astorage modulus at 0.1, 1 and 10 Hz at about 4490, about 8330 and about18800 Pa, respectively.
 3. The laminate according to claim 2 wherein theintermediate layer material has a loss modulus at 0.1, 1 and 10 Hz atabout 1840, about 4820 and about 12400 Pa, respectively.
 4. The laminateaccording to claim 3 wherein the intermediate layer material has acomplex viscosity at 0.1, 1 and 10 Hz at about 7720, about 1520 andabout 358 Pa·s.
 5. The laminate according to claim 1 wherein theintermediate layer comprises Nusil MED
 6350. 6. The laminate accordingto claim 1 wherein the base layer has a thickness of about 0.006 inchesthe intermediate layer has a thickness of between about 0.100 inches and0.120 inches and the top layer has a thickness of about 0.006 inches. 7.The laminate according to claim 1 further comprising a polyester meshlayer adjacent to the intermediate layer.